Interlaced sheet material and method



Jan. 27, 1970 P. P. A. BURNETT ETAL INTERLACED SHEET MATERIAL AND METHOD Filed April 1, 1968 RES/N, PLAS T/ C /Z ER AND OTHER /NGRED/ENTS MIX/N6 AND HOT WORK/N6 M/X TUPE OF OP/ENTED RES/N AND PLAST/C/ZEP KN/TTABL E F/LM SL/TT/NG mp5s 0F FILM OLD/N6 ND RE/NFORC/NG) m 5s READ) FOR KN/TT/NG l KN/TT/NG lw/rrm BREATHA/BLE MATER/ALI :TENTER/NG I STRESS REL/EVED AND STRETCH/5D MATER/AL PRESS/N6 v SMOOTH SURF/ICED MATER/AL COATING AER/1S /ON RES/STANTi/ZMT/MBLE STABLE MA TER/A L 4 Sheets-Sheet 1 F/ai PETEREABURNETT KELTO/V E. JANSE/V PA UL D-O'KRAV mvzu'rons ATTORNEYS Jan. 1970. P. P. A. BURNETT ETAL. 3,

INTERLACED SHEET MATERIAL AND METHOD Filed April 1, 1968 4 Sheets-Sheet 2 PE TEA PABURNE 7'7 KELTO/V E. JANSE/V P-A U1. 0- O'KRAV INVENTORS ATTORNEYS ,1970 P. P. A. BURNETT ETAL INTERLACED SHEET MATERIAL AND METHOD- 4 Sheets-Sheet 5' Filed April 1, 1968 PET M W Law &3 Kim? I A. BURNETT a N vs Jan. 27, 1970- P. P. A. BURNETT ETAL 3,

INTERLACED SHEET MATERIAL AND METHOD Filed April 1. 1968 4 Sheets-Sheet 4 WW 1 f T." FOLDED l'LL lLH Emm i i i POLYVINYL fikf Q! WES EELWSSE CHLORIDE I TAPES FOLDED POLYVINYL CHLORIDE TAPE PAUA 0. OK/PH Y INVENTORS ATTORNEYS United States Patent 3,491,560 INTERLACED SHEET MATERIAL AND METHOD Peter P. A. Burnett and Kelton E. Jansen, Mount Clemens, and Paul S. OKray, Dearhorn, Mich., assignors to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Filed Apr. 1, 1968, Ser. No. 717,554 Int. Cl. D04b 7/16 U.S. Cl. 66-202 10 Claims ABSTRACT OF THE DISCLOSURE A polyvinyl chloride resin having an inherent viscosity of about 1.31 is blended with a plasticizer, a filler, and any desired pigmentation, hot Worked, calendered into a sheet material, cut into narrow tapes, and knitted into a material particlarly suited for use as an upholstery covering for automobile seats and home furnishings. Stresses incurred during the knitting operation are relieved by uniformly heating the knitted material while its edges are pinned on a tenterframe and the face of the material is then pressed to produce a smooth surface. A protective. coating is then applied to each exposed element of the knitted material without affecting its breathability by a felt covered applicator roll. The resulting material is strong, stable, luxurious, abrasion resistant, and breathable.

SUMMARY OF THE INVENTION Most of the sheet materials previously used as upholstery coverings for automobile and household seats comprised an imprevious film of a polymeric material strengthened with a fabric backing. The tensile strength, tear strength, abrasion resistance and flexibility at high and low temperatures of these materials have been improved considerably in recent years, but the imperviousness of the material has remained to plague seat designers. Because of the imperviousness, upholstered seats were extremely warm in warm weather and extremely cold in cold weather. Luxury automobiles have turned to fabric covered seats to avoid this difficulty and achieve a more aesthetic appearance. Strength requirements and cleaning difficulties, however, have rendered this solution something less than completely satisfactory.

Numerous attempts to knit thin strips or tapes cut from a polymeric film into a breathable material suitable for upholstering automobile seats have been unsuccessful primarily because the films suitable for the knitting operating produced knitted materials having undesirable forming properties, abrasion resistance, and flexibility at low temperatures. For example, it is necessary to fold the thin tapes prior to the actual knitting operation and all attempts to uniformly fold tapes from conventional sheet materials on a production basis were unsuccessful. In addition, the materials knitted therefrom had an unsatisfactory combination of properties.

This invention provides a polymeric film readily capable of being formed into strips and interlaced into a breathable knitted material having an excellent combination of tensile strength, abrasion resistance, breathability, flexibility and aesthetic appearance. As used herein, the term interlaced is intended to include both knitting and weaving operations. The primary component of these sheet materials is a polyvinyl chloride resin having an inherent viscosity of at least about 1.28. Ordinarily, this polyvinyl chloride resin is blended With suitable amounts of an appropriate plasticizer, fillers, and pigments, and the blend is hot worked to achieve thorough mixing of the ingredients and an appropriate relationship of the plasticizer to the resin. The blend is then calendered 'ice into a relatively thin film, and the film is sliced into a plurality of narrow tapes. Tapes reinforced by being folded around a polymeric fiber having a relatively high tensile strength are then interlaced into a sheet material.

A circular knitting machine is preferably used for the interlacing operation although a wide variety of knitting or weaving operations can be used. The cylinder of knitted material resulting from the circular knitting operation is sliced longitudinally and spread out into a relatively fiat sheet. Next the flat sheet is passed through a tentering operation in which each portion of the sheet is thoroughly heated to a predetermined temperature. The tentering operation relieves stresses produced in the knitting operation to prevent curling and improve stiffness and also laterally stretches the material to reduce the weight per unit area. Thorough heating is accomplished during the tentering operation by directing streams of hot air against the sheet material; the porous nature of the material circulates the hot air around each knitted element and produces an essentially uniform temperature.

After the tentering operation the knitted material is coated with a mixture of polyvinyl chloride and polymethyl methacrylate. A felt roll is dipped in a solution of the coating material, which is applied to the knitted ma terial as the knitted materal passes between the felt roll and a rubber backup roll. Excess coating solution is removed from the felt roll by a doctor blade.

Inherent viscosities of the polyvinyl chloride resins used in the materials of this invention are determined according to the test procedure described in ASTM D-l243, method A. A. solution of 0.2 gram of the resin in cyclohexanone is used in the determination, which is performed at 30 C. Tapes made from polyvinyl chloride resins having an inherent viscosity below 1.28 cannot be folded and knited consistently and also lack the cold flexibility necessary in automobile seat coverings.

A critical step in manufacturing the sheet materials of this invention is the hot working operation. During hot working, molecules of the plasticizer surround the polymer chains of the resin and arrange the chains in a manner rendering the resulting blend more suitable for knitting. Hot working preferably is carried out in two stages with the first stage being a hot mixing operation of a relatively random nature and the second stage being a hot rolling operation. Polyvinyl chloride resins having inherent viscosities higher than about 1.35 do not readily achieve the desired arrangement of plasticizer and resin, and resins having inherent viscosities less than this value are therefore preferred. The best combination of manufacturing properties and product properties results from the use of polyvinyl chloride resins having inherent viscosities between about 1.30 and 1.33.

The tearing strength as determined by the Elmendorf method of specimens taken from the hot Worked material provides a useful indication of the degree of hot working. In the Elmendorf method, which is fully described in ASTM D689, a slit is cut in the specimen and the tearing strength along the slit is determined. Elmendorf tear strengths of at least grams per mil across the machine direction and 100 grams per mil across the transverse direction generally indicate that hot Work ing has progressed to a satisfactory point.

Cold flexibility tests are conducted on the materials of this invention by bending a test specimen of the material around a 4 diameter steel mandrel at the test temperature. Automobile seat materials capable of reasonable endurance should pass this test at test temperatures of 40 F. The mandrel is suitably supported in a cold box having a door opening at the top. A 2 x 8 inch test specimen is maintained in an air circulating oven at :5 F. for a period of 24 hours and is then conditioned at room temperature for two hours to attain moisture equilibrium. The specimen is then placed in the cold box in a planar position for 24 hours. Finally, the specimen is bent 180 around the mandrel and inspected for cracks.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a self-expanatory flow chart of the steps necessary to produce the materials of this invention. FIG- URE 2 is a side view of the heated rolls used to complete the hot working operation and perform the calendering operations. FIGURE 3 is a schematic layout of the mechanisms performing the slitting, reinforcing and circular knitting operations. FIGURE 4 is a partial side view of the arrangement used to thoroughly heat the knitted materials in the tentering and stress relieving operations. FIGURE 5 shows the equipment carrying out a pressing operation that imparts a smooth surface to the material and FIGURE 6 a side view of the coating operation. FIGURES 7 and 8 are plan and side views of a typical knitted polyvinyl chloride sheet material of the invention, and FIGURE 9 is a perspective view of the polyvinyl chloride tape folded over a reinforcing fiber used to make the sheet material.

DETAILED DESCRIPTION One hundred parts of a polyvinyl chloride resin having an inherent viscosity of 1.31, which is sold by Union Carbide Corporation under the trade name Bakelite Vinyl Resin QYSL-7, is blended with 10 parts of a water ground calcium carbonate, 3 parts of a precipitated hydrated calcium silicate, 65 parts of a plasticizer, 3.5 parts of a stabilizer, 0.5 parts of a lubricant, and 4.5 parts of a pigment. The plasticizer is made up of 6 parts epoxidized octyl tallate, 54 parts of 6-10 alfol phthalate, and 5 parts of Di-isodecyl phthalate. The stabilizer is made up of 3 parts of barium-cadmium phenates and 0.5 parts of zinc phosphite in solution. A tan color results from the pigment, which is 1.78 parts titanium dioxide, 217 parts yellow iron oxide, 0.5 parts red iron oxide, 0.05 parts carbon black. Blending is continued until the mixture is dry and free flowing.

The blend is charged to a Banbury mixer in which artificial heat and the heat generated by internal friction fuses the materials into a plastic mass. This initial phase of the hot working operation is continued until the temperature of the mass reaches at least 320 F. In place of a batch type Banbury, this phase can be carried out in a continuous type mixer in which two counter-rotating screws mix the ingredients and then force the mixture through a heated orifice to produce a continuous fused ribbon.

Hot working is continued in a steam heated mill indicated by numeral 10 in FIGURE 2. Mill 10 comprises two heated rolls 12 and 14 rotating in the indicated directions with roll 14 rotating at. a faster speed than roll 12. The plastic mass 16 is fed to the nip of the rolls and a band 18 of the plastic mass is permitted to form around the faster roll. Generaily, roll 12 rotates at a surface speed of about 65 feet per minute and roll 14 rotates at a surface speed of about 82 feet per minute. The mixture temperature reaches about 370 F. Milling is continued until strips cut from band 18 have an Elmendorf tear strength of at least 175 grams per mil across the roll direction and 100 grams per mil across the transverse direction.

A knife 19 directs a suitable portion of band 18 onto a conveyor belt 20 that carries the portion to the nip formed between rolls 22 and 24. Rolls 22 and 24 form the initial portion of the calendering operation and two additional rolls 26 and 28 are located directly below roll 24. Rolls 22, 24, 26 and 28 rotate in the indicated directions. Material passing through the nip rolls 22 and 24 is carried part of the distance around roll 24 to the nip of rolls 24 and 26. From the nip of rolls 24 and 26 a film of the material is carried part of the way around roll 26 to the nip between rolls 26 and 28 and emerges from the latter nip as a thin film 30. Film 30 preferably is about 0.005 inch thick for the best combination of knitting properties and final material properties although satisfactory knitted materials have been obtained with film thicknesses from 0.003 to 0.008 inch.

Film 30 is cooled and wound on a roll approximately 56 inches wide. This roll is sliced into a plurality of rolls about 5 inches wide, and a 5 inch roll transported to the slitting mechanism indicated in FIGURE 3 by numeral 31. In the slitting mechanism a set of drive rolls 34 and 36 unwind the film from the roll 32 and direct the film between an upper arbor 38 and a lower arbor 40 that slit the film into a plurality of thin tapes 42. A second set of drive rolls 44 and 45 draw the tapes across a lubricating roll 46 positioned between two guide combs 47 and 48. Lubricating roll 46 has its lower portion immersed in an open tank 49 containing a water solution of sulfonated castor oil and emulsified paraffin wax. Rolls 44 and 45 direct the tapes to the circular knitting machine indicated in FIGURE 3 by numeral 50.

Each tape entering the knitting machine 50 passes through a stop motion device indicated generally by numeral 52. Stop motion device 52 comprises a spring member 54 tensioned into an unstable position by the tension existing in tape 42. If tape 42 should break, the tension holding spring member 54 is released and the spring member returns to a neutral position, thereby tripping a switch (not shown) that shuts down the slitting and knitting machines. The tape then passes through appropriate guides 56 and 58 and is directed through a folding mechanism 59.

Folding mechanism 59 comprises a plate 60 having a spring steel arm 61 attached thereto. Arm 61 projects downward in the direction of movement of the tapes and has a hole 62 formed in its lower end. Hole 62 has a diameter equal to or slightly smaller than the tape width, and as the tapes pass through hole 62, the edges thereof are folded toward each other. Just prior to the point where the tape enters hole 62 a nylon reinforcing yarn 66 is directed to one side of the tape so the folding action folds the tape around the yarn 66. Yarn 66 has a denier of at least about 70. The folded and reinforced tapes are then knitted on the circular knitting machine.

A large cylinder of knitted material is formed by the knitting machine. This cylinder is wound onto a roll and transported to the entrance of a tentering mechanism. As the knitted material is unrolled, it is sliced longitudinally and spread out into a substantially flat sheet. The edges of the sheet then are pinned onto a tenterframe such as that shown in U.S. Patents Young 2,429,- 177 or 2,473,404, for example, and the tenterframe transports the sheet into a treating oven.

FIGURE 4 is a partial perspective view of the heating zone in the oven. As the material, represented in FIG- URE 4 by numeral 68, passes into the heating zone, hot air issues from a plurality of pipes 70 and 72v located above and below material 68 respectively. The hot air is directed onto the material at an angle substantially perpendicular to the plane of the material with sufiicient velocity to circulate through the pores formed in the knitting operation. This circulation provides essentially uniform heating of material 68, which preferably reaches a temperature of about 275 F. for good stress relief. The pipes in each upper row in the heating zone are spaced laterally 2 /2 inches center to center (dimension a in FIGURE 4) and each pipe has an inside diameter of /2 inch. Each succeeding row is spaced 3 inches downstream from its preceding row (dimension b) and each pipe of the succeeding rows is laterally displaced about /2 inch from the pipes in the preceding row (dimension 0). The ends of the upper pipes are located about 3 inches above the surf-ace of the sheet material, and the hot air issues from the upper pipes at a velocity of about 6,000 feet per mlnute.

The pipes in each of the lower rows are spaced laterally 5% inches center to center (dimension d) and each lower pipe has an inside diameter of inch. Succeeding rows of lower pipes are about 5 inches downstream from each previous row (dimension e), and the pipes in each succeeding row are laterally displaced about 1 inch from the pipes in the previous row (dimension 1). The ends of the lower pipes are about 8 inches below the surface of the sheet material, and the hot air issues from the lower pipes at a velocity of about 7,000 feet per minute.

A typical heating zone is about 13 feet long and the sheet material moves through the heating zone at about 80 feet per minute. Up to 12 percent of lateral stretching can be performed in conjunction with the stress relieving operation by including a second heating zone in which the sides of the tenterframe move laterally outward. The second heating zone is constructed in the same manner as described above and immediately follows the stress relieving zone.

Lateral stretching continues in a dormant zone about 12 feet long and the material then passes into a cooling zone in which the tenterframe sides again move parallel to each other.

The material then passes through a pressing operation that imparts a smooth texture. Referring to FIGURE 5, a rubber roll 74 is positioned next to a drum 76 that is 36 inches in diameter and is heated by steam. On the other side of the drum are two Teflon coated rolls 78 and 80 that are also heated by steam. A steel pressing roll 82 and a rubber backup roll 84 are located below roll 80. An idler roll 86 is positioned adjacent pressing roll 82.

Rubber roll 74 applies the face of the material 68 to the surface of roll 76 and the material face stays in contact with roll 76 for at least 180 of rotation. Upon leaving roll 76, the back of material 68 wraps partially around roll 78 and then the face again contacts roll 80. Material leaving roll 80 has a face temperature of about 300 F., and the material then passes between rolls 82 and 84 with the face contacting roll 82. Rolls 82 and 84 exert a pressure on the material suflicient to smooth the face by flowing the polyvinyl chloride; for best resnlts, the pressure must be determined empirically. Roll 82 is water cooled to a surface temperature of less than about 100 P. so the face of the material is chilled before the material leaves roll 82. The material then passes over idler roll 86 and is directed into a cooling chamber (not shown).

A protective coating is then applied to the exposed elements of the sheet material by the apparatus shown in FIGURE 6. An applicator roll 94 is fabricated by positioning a fibrous sleeve 96 on a steel core 98. The fibrous sleeve is less than about 0.25 inch thick and best results are obtained with a wool felt sleeve about 0.10 inch thick. A rubber backup roll 100 is positioned adjacent applicator roll 94 and the sheet material 68 is passed between applicator roll 94 and backup roll 100.

Applicator roll 94 is rotated at a speed of about 50 feet per minute in an 8-10 percent by weight solution 102 of polyvinyl chloride and polymethyl methacrylate. Approximately 75 percent of the solids in the solution are polyvinyl chloride with the remainder polymethyl methacrylate. Methyl ethyl ketone can be used as the solvent. A doctor knife 104 positioned adjacent the exterior periphery of applicator roll 94 removes excess solution from the sleeve. As the sheet material passes between rolls 94 and 100, the solution is applied to each exposed element of the material without significantly decreasing the breathability of the material. After the coating solution is applied, the sheet material 68 enter a drying oven 106 maintained at about 300 F. About 0.2 ounce of coating composition is applied per square yard of sheet material. The resulting coating blocks plasticizer migration from the materials, improves the abrasion and soil resistance, and produces a uniform, controlled gloss.

The resulting sheet material weighs about 30 ounces per square yard and has an excellent combination of tensile strength, cold flexibility, and cold impact resistance. :In aesthetic appearance and feel, the material ranks With more expensive and less durable natural or synthetic cloth. The breathability of the material runs about 2,000 cubic inches per second per square inch, which exceeds all materials previously used as automobile seat coverings.

What is claimed is:

1. An interlaced material formed from folded tapes, said tapes consisting essentially of a polyvinyl chloride resin having an inherent viscosity between about 1.28 and 1.35 blended with a plasticizer wherein the molecules of the plasticizer substantially surround the molecules of the polyvinyl chloride resin to produce tapes having an Elmendorf tear strength of at least grams per mil.

2. The material of claim 1 comprising about 55 to 70 parts of plasticizer per hundred parts of polyvinyl chloride resin.

3. The material of claim 2 in which the inherent viscosity of the polyvinyl chloride resin is about 1.30-1.33.

4. The material of claim 3 in which the tapes are reinforced with a thread of a polymeric material having a denier of at least 70.

5. The material of claim 1 in which the tapes are reinforced with a thread of a polymeric material having a denier of at least 70.

6. The material of claim 5 in which the polyvinyl chloride resin has an inherent viscosity of about 1.30-1.33.

7. A process for producing an interlaced material from polyvinyl chloride film comprising:

blending polyvinyl chloride resin having an inherent viscosity of at least about 1.28 with a plasticizer,

hot working the blend until the tearing strength of a specimen conducted according to the Elmendorf Method is at least grams per mil across the machine direction and 100 grams per mil across the transverse direction,

calendering the blend into a film,

slitting the film into narrow tapes,

folding the tapes on a reinforcing fiber, and

interlacing the reinforced tapes into a sheet material.

8. The process of claim 7 in which the inherent Viscosity of the polyvinyl chloride resin is less than about 1.35.

9. The process of claim 8 in which the inherent viscosity of the polyvinyl chloride resin is about 1.30-1.33.

10. The process of claim 9 in which interlacing is a circular knitting operation.

References Cited UNITED STATES PATENTS 3/1964 Lefevre et al 57-151 X 7/ 1967 Marks 66202 US. Cl. X.R. 

